Mini-grids powered by renewable energy sources have periods of high and low energy production due to variability in resources. The reliability of power supplied from such systems can be significantly improved by incorporating energy storage systems. This study investigates the use of energy storage – pumped hydro systems and hydrogen fuel cells – in a mini-grid system for operational cost reduction and system reliability improvement. The hybrid system’s power output is modelled with the objective of simultaneously minimising fuel costs while ensuring system reliability. The proposed mathematical model is verified using realworld data of KwaZulu Natal site in South Africa. The simulation results show that small-sized pumped hydro systems (PHS), in combination with Hydrogen Fuel Cells (HFC) can significantly reduce fuel costs of diesel generators in off-grid systems by 69% in summer and 34% in winter
Keywords Hybrid energy storage, pumped hydro storage, hydrogen fuel cells, renewable energy.